The present invention relates generally to operations performed in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides a method of monitoring a well using annulus pressure manipulations.
Various methods have been used in the past for remotely communicating with a downhole location. For example, electromagnetic telemetry, acoustic telemetry, mud pulse telemetry during drilling operations, etc. However, each of these methods has its drawbacks when used for permanent well monitoring.
Electromagnetic and acoustic telemetry each require a downhole power source, such as a battery. The downhole power source is needed to power downhole electronic circuits and sensors. The actual transmission of electromagnetic or acoustic waves from a downhole location to a remote location, such as the earth's surface, requires a substantial amount of power.
If this power is supplied by batteries, then they will need to be frequently refreshed or recharged. This will necessitate intervention into the well and interruption of the production flow from the well, each of which is costly. If the power is supplied by lines extending into the well, the lines are costly to install and are subject to damage throughout the productive life of the well.
Mud pulse telemetry requires a circulating fluid flow. In a producing well, fluid typically flows upward through a tubing string, and an annulus surrounding the tubing string is maintained at a static pressure, with no communication between the tubing and the annulus. Power to operate the downhole mud pulse telemetry equipment may be supplied by batteries, by lines extending to the surface, or by the fluid circulation. However, as discussed above, batteries and lines extending to the surface have certain drawbacks when used for long term well monitoring, and fluid circulation is not available.
Therefore, it may be seen that there is a need for a method whereby a well may be conveniently and economically monitored on a long term basis. Methods and equipment suitable for this purpose could also be used for other purposes.